Activate Karn's Bastion's last ability by paying {4} and tapping it, putting an eon counter on Magosi.
Activate Nesting Grounds's last ability by paying {1} and tapping it, moving an eon counter from Magosi to Nesting Grounds.
Activate Magosi's last ability by tapping it, removing an eon counter from it, and returning it to your hand, taking an extra turn after this one.
Play Magosi from your hand.
Move to your next turn.
Activate Karn's Bastion's last ability by paying {4} and tapping it, putting an eon counter on Nesting Grounds.
Activate Nesting Grounds's last ability by paying {1} and tapping it, moving an eon counter from Nesting Grounds to Magosi.
Repeat from step 3.

Infinite turns

Magosi, the Waterveil

Nesting Grounds

Karn's Bastion

Activate Nesting Grounds's last ability by paying {1} and tapping it, moving an eon counter from Magosi to Nesting Grounds.
Activate Magosi's last ability by tapping it, removing an eon counter from it, and returning it from the battlefield to your hand, taking an extra turn after this one.
Play Magosi.
Evolution Sage triggers, causing you to proliferate, putting an additional eon counter on Nesting Grounds.
On your next extra turn, activate Nesting Grounds's last ability by paying {1} and tapping it, moving an eon counter from Nesting Grounds to Magosi.
Repeat from step 2.

Evolution Sage

Activate Contagion Engine by paying {4} and tapping it, putting an eon counter on Magosi.
Activate Nesting Grounds's last ability by paying {1} and tapping it, moving an eon counter from Magosi to Nesting Grounds.
Activate Magosi's last ability by tapping it, removing an eon counter from it and returning it to your hand, taking an extra turn after this one.
Play Magosi from your hand.
Move to your next turn.
Activate Contagion Engine by paying {4} and tapping it, putting an eon counter on Nesting Grounds.
Activate Nesting Grounds's last ability by paying {1} and tapping it, moving an eon counter from Nesting Grounds to Magosi.
Repeat from step 3.

Contagion Engine

Activate Contagion Clasp by paying {4} and tapping it, putting an eon counter on Magosi.
Activate Nesting Grounds's last ability by paying {1} and tapping it, moving an eon counter from Magosi to Nesting Grounds.
Activate Magosi's last ability by tapping it, removing an eon counter from it and returning it to your hand, taking an extra turn after this one.
Play Magosi from your hand.
Move to your next turn.
Activate Contagion Clasp by paying {4} and tapping it, putting an eon counter on Nesting Grounds.
Activate Nesting Grounds's last ability by paying {1} and tapping it, moving an eon counter from Nesting Grounds to Magosi.
Repeat from step 3.

Contagion Clasp

At the beginning of your upkeep, Out of the Tombs triggers, putting two eon counters on itself, then milling cards equal to the number of eon counters on it.
Activate Nesting Grounds by paying {1} and tapping it, moving an eon counter from Out of the Tombs to Magosi.
Activate Magosi by tapping it, removing an eon counter from it, and returning it to your hand, causing you to take an extra turn after this one.
In your main phase, play Magosi.
Go to your next turn.
Repeat.

Out of the Tombs

Activate Nesting Grounds's last ability by paying {1} and tapping it, moving an eon counter from Magosi to Nesting Grounds.
Activate Magosi's last ability by tapping it, removing an eon counter from it, and returning it from the battlefield to your hand, taking an extra turn after this one.
Play Magosi.
At the beginning of your end step, Atraxa triggers, causing you to proliferate, putting an additional eon counter on Nesting Grounds.
On your next extra turn, activate Nesting Grounds's last ability by paying {1} and tapping it, moving an eon counter from Nesting Grounds to Magosi.
Repeat from step 2.

Atraxa, Praetors' Voice

Play The Mirari Conjecture and Time Warp, then go to the next turn.
Use Conjecture's 2nd activation to add Time Warp back to hand, then play Nesting Grounds.
Play Time Warp.
Go to the next turn.
Activate Nesting Grounds to remove a saga counter from Conjecture, then add back Time Warp when Conjecture's 2nd activation triggers again.

The Mirari Conjecture

Time Warp

Tap Kilo by any method, triggering Kilo, causing you to proliferate and put an eon counter on Magosi.
Activate Nesting Grounds' second ability by paying {1} and tapping it, moving an eon counter from Magosi onto Nesting Grounds.
Activate Magosi's third ability by tapping it, removing an eon counter from it and returning it from the battlefield to your hand, causing you to take an extra turn after this one.
Play Magosi.
Move to your next turn.
Tap Kilo by any method, triggering Kilo, causing you to proliferate and put an eon counter on Nesting Grounds.
Activate Nesting Grounds' second ability by paying {1} and tapping it, moving an eon counter from Nesting Grounds onto Magosi.
Repeat from step 3.

Kilo, Apogee Mind

Play The Mirari Conjecture and Temporal Manipulation, then go to the next turn.
Use Conjecture's 2nd activation to add Temporal back to hand, then play Nesting Grounds.
Play Temporal Manipulation.
Go to the next turn.
Activate Nesting Grounds to remove a saga counter from Conjecture, then add back Temporal when Conjecture's 2nd activation triggers again.

Temporal Manipulation

Play The Mirari Conjecture and Capture of Jingzhou, then go to the next turn.
Use Conjecture's 2nd activation to add Capture of Jingzhou back to hand, then play Nesting Grounds.
Play Capture of Jingzhou.
Go to the next turn.
Activate Nesting Grounds to remove a saga counter from Conjecture, then add back Capture of Jingzhou when Conjecture's 2nd activation triggers again.

Combos with "Nesting Grounds"